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Shanghai's skyline glitters with sleek financial skyscrapersand glossy residential towers, but below the city s lustrousfacade lies an enduring problem. Thanks to mass urban migration,soft soil and global warming , Shanghai is sinking, and has been for decades. Since 1921, China s most populous city has descended more than 6 ft. Across China,land subsidence affects more than 50 cities , where 49,000 sq. mi. of land have dropped at least 8 in. It's not just the numbers that are frightening: the problemhas manifested itself tragically and more frequently of late.Earlier this month, a young woman unexpectedly fell through the sidewalk into a 20-ft.-deep sinkhole while walking along the street inXi'an. In late April, a woman died after falling through thesidewalk into a pit of boiling water in Beijing. Scientists havecontinuously warned of dire repercussions if the government doesnot implement more stringent guidelines for urban planning, waterusage and carbon emissions and they expect the situation to getmuch worse in areas with large-scale, fast-paced construction, likeShanghai. As progress continues on Asia s soon-to-be-tallest skyscraper, theShanghai Tower, the problem has manifested itself in maliciouscracks nearby, captured and posted by users of the Twitteresque microblogging site Sina Weibo. Inmid-February, one blogger posted about a 22-ft.-long crack situatednear the 101-story Shanghai World Financial Center, across thestreet from the highly anticipated tower. ( MORE: A Valuable New Tool Lets You See Where the Sea Will Rise ) In response to bloggers concerns, Shanghai Tower Construction,the company responsible for building the tower, issued a statementsaying surface cracks were controlled and safe, theShanghaiist reported . Liu Dongwei, chief architect of the China Institute of BuildingStandard Design & Research, cited groundwater, rainfall andsoft soil foundation as the reasons for the settlements. Butthat's only partially accurate. Shanghai has inherently soft soil because of its geographicalposition at the mouth of the Yangtze River basin and, yes,groundwater accounts for nearly 70% of land subsidence; however,experts say , the weight of skyscrapers and global warming also play heftyroles in aggravating what they call "the most importantgeological disaster in Shanghai." Unfortunately, theimplications will only grow graver with the pace of development andrising sea levels. According to a report by the Shanghai Geological Research Institute, the physicalweight of skyscrapers accounts for 30% of Shanghai's surfacesubsidence. Usually groundwater pumping is the key factor, Jimmy Jiao, a professor of earth sciences at Hong Kong University, tells TIME. But in Shanghai, development is alsoimportant because the building density is high, and most of thehigh-rise buildings are sitting on the areas with soft soil. Basically, what's happening is, the weight of high-risetowers presses down on the earth, as if you were to put a weight ona spring or scale. ( MORE: Tourists Foot the Bill to Keep Venice Above Water ) The most densely packed city in China, Shanghai reached apopulation of 23 million in 2010, according to census data . With the soaring number of denizens flocking to the seaside city,developers have stacked more than 50 skyscrapers and thousands ofhigh-rises side by side like dominoes. The country as a whole built200 new skyscrapers in 2011, and by 2016, the total number isexpected to exceed 800. "As the saying goes, the more you build, the more theycome," Jiang Li, a professor of civil engineering atBaltimore's Morgan State University who grew up in Tianjin,China, tells TIME. Pretty soon there will be 30 millionpeople in Shanghai, while Beijing is just short of 20 millionpeople. At this point, so much construction has already been donethat the areas are hopeless," hesays. Today's problems have been aggravated by decadesof overdeveloping and overpumping of groundwater resources. The problems began in the 19th century, when Shanghai transformedinto a trading port and began attracting both immigrants andChinese transplants. By 1900, the population had tripled to morethan 1 million. People started consuming more groundwater than theoverlying turf could handle, and the problem worsened dramatically.By the 1950s and 60s, the area started sinking 4 in. peryear. Since then, the city has descended more than 16 in.,despite government bans on wells and efforts to pump water backinto underground reservoirs. Every day, Shanghai is redirecting60,000 tons of water through 121 wells, China Daily reported . ( MORE: Welcome to the Era of the Everyday Billion-Dollar Disaster ) Shanghai may have had this problem before the 1950s, but it didn tstart emerging in other cities until the early 80s. Now more than50 cities across the country face sinking problems, according to a report by the China Geology Survey. Three regions in particular have serious land-subsidence problems, including the Yangtze Riverdelta area, the Fenhe River Weihe River basin and the North ChinaPlain. According to CCTV , Cangzhou, a city in north China's Hebei province, hasdescended nearly 7 ft. In 2009, the city had to demolish athree-story building housing a branch of the city'sPeople's Hospital because the first level sank so low that itfell underground. Though some critics argue that the Chinese government has been tooslow to act, research, public concern and some hefty bills ($35billion in Shanghai alone in the past 40 years) have sparked some momentum. Recently thestate council approved China's Land Subsidence Prevention Project, a countrywideinitiative to prevent land subsidence. Likewise, Beijing, which hasdescended more than a foot in the past decade, has also made aneffort to reduce underground-water extraction, with plans to close800 water-extraction wells this year, according to the BeijingWater Authority. By 2014, the city hopes to halt underground-waterextraction in urban areas altogether as part of the North-SouthWater Diversion Project. The project expects to deliver 3 billion cu. ft. of water supply to Beijing from theYangtze River. This would not only satisfy one-third of the city stotal water demand but would also cut the extraction of undergroundwater in half. But Li, who worked at the Chinese Academy of Science for 15years, says such programs will not be enough. It s hard toquantify how much this might help, but the question is, Is that aproblem solved? The answer is no. The problem lies in the earlyissue with urbanization, he says. Scientists expect theregulations to help curb the consumption of underground-watersupplies, but there a few things the government has less controlover, like global warming. As land degradation and excessiveguzzling of groundwater continue, environmentalists predict waterssurrounding Shanghai will rise 9 to 27 in. by 2050 as a result ofmelting ice caps. ( PHOTOS: With an Eye to the Future, Shanghai Dismantles Its World Expo Site ) If you look at Shanghai during high tide, you can see the waterlevel is higher than the streets but separated by the wall,"Li says. "This is a situation where if you have a majordisaster like a hurricane, tsunami or tropical storm, it can causeserious damage." He is especially worried about severeflooding in the coastal areas, where the majority of Chinesemigrants have settled. The only way to really solve the problem isto reduce or better yet, stop groundwater pumping. Anotheroption is to decrease the density of buildings, which would meanfewer heavy skyscrapers, perhaps an unrealistic solution forChina s rapidly growing cities. In the meantime, Li suggests local governments impose waterrestrictions and fees to encourage less wasteful consumption ofwater. He also proposes more secondary water uses, where wastewateris recycled for washing cars or watering plants. Even then, globalwarming remains an obstacle. As skyscrapers in Shanghai go up andthe glaciers in the North and South poles melt down, cities likeShanghai grow more and more vulnerable every day. We are high quality suppliers, our products such as Fish Attracting Lights , 0603 SMD LED Manufacturer for oversee buyer. To know more, please visits 3528 SMD Leds.
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